Act I
Scene 1: Popular festival, until Flavius and Marullus (Tribunes) send the common people home, telling them not to celebrate Caesar's victories. Then they take ornaments off the statues.
Scene 2: Soothsayer warns Caesar of the Ides of March. During a ritual race, Cassius and Brutus talk, begin to conspire. Caesar returns, angry. Casca tells Brutus and Cassius that Antony offered him the crown three times, but he refused and the people cheered.
Scene 3: Casca and Cicero meet in the storm, talk of signs. Cassius and Casca conspire. Cinna too.

Act II
Scene 1: Brutus at home; letter found thrown through window (by Cassius). Brutus meets the conspirators, they plan to kill Caesar. Brutus refuses to have Antony killed too. His wife Portia heroically demands to share his plans.
Scene 2: Caesar reports Calphurnia's words in her sleep. Orders sacrifices, hears tales of night's horrors. Bad signs in sacrifices. Calphurnia begs him not to go out. He accepts, but when Decius offers another interpretation of her dream, Caesar decides to go. Conspirators come to fetch him.
Scene 3: Artemidorus writes a letter to warn Caesar.
Scene 4: Portia anxious for news.

Act III
Scene 1: Proud Caesar does not read Artemidorus's warning. The conspirators gather round and kill him. People shocked. "Peace, freedom and liberty". They dip their hands in the blood. Antony sends message asking to hear why Caesar had to die. Antony comes, offers to die if necessary. He shakes their hands, then praises Caesar. He asks to speak to the people at the funeral. Brutus allows this despite Cassius. Antony's soliloquy on "Caesar's spirit, ranging for revenge." Sends messages to Octavius.
Scene 2: People demand explanations, Brutus speaks, convinces them he did right. Antony comes with the body, "Friends, Romans, countrymen, lend me your ears!" Stirs the people to other opinions. Reads the will of Caesar "If you have tears..." People in mutiny; Octavius comes into Rome, Brutus and Cassius leave it.
Scene 3: Death of the wrong Cinna at the hands of the angry mob.

Act IV
Scene 1: Antony, Octavius, Lepidus decide unsentimentally who must die, even in their own families, discuss political morality. Preparations for war with Brutus and Cassius.
Scene 2: Brutus and Cassius in disagreement about money and bribes.
(Scene 3): Brutus very angry, Cassius threatens suicide, Brutus gives in, they are reconciled. News of Portia's death had made Brutus wild. News of Antony and Octavius. They prepare for battle at Philippi. Brutus works late, sees the ghost of Caesar.

Act V
Scene 1: Octavius and Antony arrive with their army at Philippi. They encounter Brutus and Cassius, challenge them. Cassius reports bad omens. Brutus and Cassius say farewell, feeling foreboding.
Scene 2: Battle. Brutus sees hope of victory.
Scene 3: Cassius's army flees. Cassius commits suicide: "Caesar thou art reveng'd," too early, for Brutus has won his side of the battle. Titinius kills himself to be with him. Brutus comes, speaks.
Scene 4: Brutus is nearly caught.
Scene 5: Brutus sees he has lost the battle; runs on his sword: "Caesar now be still." Antony and Octavius arrive. "This was the noblest Roman of them all."

The title of the play presents a problem, for Caesar is killed at the beginning of Act III, without having been on stage long enough for us to sense the deeper aspects of his character. In many ways, the play's protagonist is Brutus, it represents his fall, and he is brought down by the spirit of Caesar. Brutus is an idealist in a political world where other laws govern, he lacks the skill to dominate the course of history. After Brutus, Antony (in Antony and Cleopatra) will suffer a similar defeat, and the way will be open for Octavian to become the first Emperor, Augustus, under whose dictatorial reign the Roman empire took shape.

Brutus is representative of older republican values, of trust and simple honesty. He cannot see that the age in which he lives demands other forms of government to control the violence of mobs and usurpers. This is shown above all by the political error he makes in allowing Antony to address the fickle crowd of Romans; he sincerely thinks that the conditions he has imposed will be enough to prevent any damage. Antony, then, launches out on the great speech for which this play has long been famous.

In this play, as in his other Roman plays, Shakespeare strives to represent an ethos alien to his own age. The stress on personal honor and on civic virtues, the absence of Christian dimensions, and the use of heroic suicide are all features derived from the source in Plutarch. The political dimension is a clash between the Republican ideals represented idealistically (but unrealistically) by Brutus's attitudes, while the other Conspirators represent ambition, opportunism and anarchy. Caesar seems to represent the imperial model of power, by the authority he has acquired in life, although he refuses the crown Antony offers him. The audience knows what will follow in a few years' time, and there is sharp irony in the way Antony speaks the eulogy of Brutus's Roman virtues at the end of the play, for in Antony and Cleopatra, Shakespeare was to show Antony turning his back on Roman nobility in order to follow the exotic queen of Egypt:

This was the noblest Roman of them all.
All the conspirators save only he
Did that they did in envy of great Caesar;
He only, in a general honest thought
And common good to all, made one of them.
His life was gentle, and the elements
So mix'd in him, that Nature might stand up
And say to all the world, "This was a man!" (Act V.v)

It is not by chance that Hamlet, written just after this play, is full of the question of what it takes to be a Man.